Cloud-Point Extraction for On-Line Trace Determination of Copper(II) by Flame Atomic Absorption Spectrometry

Abstract

A cloud point extraction-flow injection procedure is proposed for on-line determination of trace amounts of copper(II) by flame atomic absorption spectrometry. Copper(II) was extracted using the non-ionic surfactant, Triton X-114 after complex formation with N-phenyl benzohydroxamic acid at pH 5 in the presence of sodium sulfate as a salting-out agent at 25 °C. After the cloud point having been obtained in the reaction coil at room temperature, the surfactant-rich phase containing the complex was collected in a mini-column packed with cotton. Then, the complex was eluted into the nebulizer of flame atomic absorption spectrometer by passing ethanol containing 1% (v/v) nitric acid. The chemical and flow variables including pH, reagent and surfactant concentrations, sample and eluent flow rates affecting the extraction and determination were optimized and the enhancement factor was estimated to be 45. The sample throughput (15 h-1) was greater than batch technique. The calibration graph was linear in the range of 5–220 μg l−1. A good precision for 50 μg l−1 copper(II) (1.9% RSD, n = 8) and detection limit (3Sb m−1) 1.00 μg l−1 were obtained. The accuracy was assessed by the analysis of a standard reference material (NBS-364) and the obtained results were in good agreement with certified amounts of copper. The proposed method was applied to the determination of copper(II) in water and hair samples.